I mean, my most crappy meter goes down to 0,001 micro volts?
Errr, you sure you have instrument that has resolution of 1 nano Volt ? 0,000000001 V ?
Apart from that, Kleinstein is, as usual, right. Absolute accuracy is important when you work with other people. It is same thing as standardizing other measurements, in other industries.
For instance, if I buy a 3mm pin, what actual size it will be? If I buy 3mm pin from Japan, and a 3mm drill from Germany, will the pin fit in the hole? Will it be too small or too big?
That was the whole point of standardization effort in industrial revolution. Same here.
And same as mechanical problems, it will be important how accurate that 3mm is based on that what you do. Optical lens holder for accurate laser system will obviously have to be more precise and accurately made than garden tool.
In general, mostly you don't need better accuracy or resolution than what good handheld meters provide. When you do, you will know. It will be fairly obvious as a part of the problem you're solving.....
I'm a firm believer in not buying stuff for your lab (privately or work) that you won't use... There are few things you have to have (some decent handhelds, some kind of oscilloscope that covers kind of work you do, some power sources, some signal sources), all other equipment comes as requirement of your work...